• Journal of the Korean Wood Science and Technology
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• v.17 no.3
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• pp.67-81
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• 1989

This experiment was carried out to know the mothod of changing the step of moisture content schedule with time in conventional kiln drying. For the purpose of this object. we made drying model by applying the moisture diffusion model by J.FSiau(1984) to average moisture content equation by J.Crank(1956) derived it from Fick's second law. And to verify this method of drying model. 2.5cm-thick boards and 5.0cm-thick dimension lumbers of Pinus densiflora were kiln-dried with the schedule of T11-C3 and T10-C4, respectively. And then the drying rates were investigated and compared with those calculated from drying model. The results obtained were as follows 1. Average drying rate and total drying time of board to dry to 6.5% moisture content were 0.64%/hr and 109hr., and those of dimension lumber to dry to 8.3% moisture content were 0.4%/hr. and 162hr., respectively. 2. The moisture content of shell and core decreased by equalizing treatment and increased by conditioning treatment both on board and dimension lumber. But the moisture gradient was lower after conditioning than after equalizing. 3. As the drying was proceeded, the transverse bound water diffusion coefficient all but linearly decreased, the water vapor diffusion coefficient abruptly curvilinearly increased, while the transverse diffusion coefficient curvilinearly decreased both on board and dimension lumber. But each of diffusion coefficients on board was larger than that on dimension lumber. 4. Compared to experimential drying rate of board. theoretical drying rate was larger at 30.0%-21.8% moisture content range and was similiar at 21.8%-5.4% moisture content. And in case of dimension lumber, the drying rate was similiar at 30.0%-16.1% moisture content range but theoretical drying rate was much lower at 16.1%-8.3% moisture content range. 5. The possibility of adapting this drying model to changing the moisture content schedule step with time was in the range of 21.8%-5.4% moisture content on board. And in the case of dimension lumber that was in the range of 30.0%-16.1% moisture content.

• Journal of the Korean Wood Science and Technology
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• v.40 no.4
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• pp.257-267
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• 2012

In this study, the method for heat treating wood using superheated steam (SHS) was designed and applied. The physical and mechanical properties of Korean Pine (Pinus koraiensis Siebold & Zucc.) lumber heat-treated by SHS at $170^{\circ}C$ and 0.4 MPa for 10 hours were compared with those of non-treated and normal heat-treated wood. The amount of adsorbed water and equilibrium moisture content of the SHS treated wood were lower than non-treated wood. On the other hand the compressive strength parallel to grain and the bending strength of SHS treated wood were higher than those of non-treated wood. The hygroscopicity of SHS treated wood was similar to normal heat treated wood at $220^{\circ}C$. Internal checks that often occur during normal heat treatment were not developed at SHS treatment. Also, SHS treatment are effective in control of internal checks occurrence and resin exudation.

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.780-790
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• 2020

In this study, the cell-wall microstructure and anti-swelling effectiveness (ASE) of heat-treated larch wood were evaluated and the correlation between them was analyzed. For this purpose, some larch lumbers were heat-treated for 12, 18, and 24 hours at temperatures of 190℃ and 220℃. By observing the scanning electron microscopy cross-sectional image of the heat-treated larch, it was confirmed that the shape of heat-treated wood cell changed, the cut-section of the wood cell wall was rough, and the intercellular space has become wide as the intercellular bonds had broken because of heat-treatment. In addition, the evaluation of the swelling for each treatment condition revealed that, as the heat-treatment temperature and duration increased, the amount of absorbed water and swelling decreased and the ASE increased. The decrease in the amount of absorbed water is thought to be affected by the chemical change in the cell wall by heat-treatment. On the contrary, the decrease in the swelling and the increase in the ASE are thought to be due to a combination of chemical changes and physical changes such as structural changes in the cell wall.

• Journal of the Korea Furniture Society
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• v.21 no.6
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• pp.486-498
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• 2010

The purpose of this study was to analyze the species of 82 furniture in the late Choseon Dynasty (mainly, 19th century), which are housed in the Seoul Museum of History. Total of 22 species were found. The species shared 43% as hard pine(Diploxylon), 9% as Zelkova serrata Makino, 7% as Paulownia spp., 7% as Tilia spp., 6% as soft pine(Haploxylon), 5% as Ginkgo biloba Linn., 4% as Cedrela sinensis A. Juss., 3% as Diospyros spp., 3% as Abies spp., 2% as Alnus spp., 2% as Picea spp., 1% as bamboo, 1% as Populus spp., 1% as Betula spp., 1% as Juglans spp. The other minor ones were Torreya nucifera Sieb. et Zucc., Pyrus spp., Castanea spp., Ulmus spp. and Kalopanax oictuse (Thunb.) Nakai. Thirty seven furniture (45% in total) was made of single species, 19 (23%) of two species, 16 (20%) of three species and 10(12%) of 4 to 6 species. For frames and panels, hard and strong woods, such as hard pines, Zelkova and Cedrela, were used. For drawer, however, light woods having low shrinkage, such as Paulownia and Tilia, were used. The origin of woods could be specified by the habitats of the species identified. Both Hwanghaedo- and Parkcheon- Chests used basswood (Tilia), which grow in the cold regions, indicating the origin of woods as North Korea.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.3
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• pp.614-618
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• 2018

The changes in the mechanical properties according to the width of the tool shoulder, rotation speed and moving speed in friction stir welding (FSW) are evaluated using Al 6061-T6. The results indicated that the tensile strength value increases with increasing rotation speed. The higher the moving speed of the tool shoulder, the lower the tensile strength, regardless of the tool type. A higher tensile strength value was generally obtained with a tool shoulder diameter of 12mm (TSD12) than with 8mm. When the moving and rotation speeds exceed a limiting value, a stabilization stage is reached, in which (the tool shoulder diameter?) no longer affects the material properties. At a tool shoulder diameter of 8mm (TSD8), the material properties are decreased and the mixture of material in the welding area is incomplete in comparison with the tool type of TSD12. The tensile strength value is decreased at a rotation speed of 1500 rpm. As a result, a rotation speed higher than the threshold value is needed in order for and the transition temperature to be reached, which allows the complete mixing of the material in the welding area.

• Journal of the Korean Wood Science and Technology
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• v.45 no.5
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• pp.622-628
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• 2017

In order to develop value-added utilization technology of domestic oaks the processing yield rate from the standing tree to the flooring material for the Quercus variabilis and Quercus mongolica were investigated. Also, to reduce drying time, improved drying schedule was applied and the physical properties were measured. The drying time was 173 hours in total, and the final moisture content was 5.39% (Quercus variabilis) and 4.17% (Quercus mongolica). The color difference of oak lumber before and after drying showed a significant change as ${\Delta}E$ value from 7 to 11. The shrinkage rates of Quercus variabilis and Quercus mongolica during drying were 8.1% and 8.5% in the tangential direction and 5.0% and 6.2% in the radial direction, respectively. The lumber manufacturing yield rate of sawn lumber was 30 to 40% and that of the final product was 8 to 15%. It is expected that the processing characteristics of the Quercus species investigated in this research could contribute to formulate an efficient production plan of domestic hardwoods that are still under utilization.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.49-55
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• 2017

Most motor cases adopt deep drawing products, which are excellent in waterproof functions, concentricity, right angle, and quality. In addition, the blower motor and seat motor, which are installed in the car interior and do not require waterproof function, adopts a multi-forming manufacturing method. The deep drawing process requires an expensive transfer press that can digest approximately 12 processes, such as drawing, trimming and piercing. On the other hand, products can be produced with low investment because the multi-forming method is composed of one multi-forming machine or one multi-forming machine and one press. The multi-forming machine is a high-priced facility that is mostly imported and a bending / shearing process multi-foaming machine, which was developed by domestic small and medium-sized enterprises, is not enough to reduce the production cost. An integral multi - forming machine is used as a limited working method for thin material and small products. A large product and thick material has a high shear load. A large product and thick material has a high shear load and uses a single crank press. After blanking, the worker manually feeds the material to a multi-forming machine. When the bending operation is performed in the multi-forming machine, it is transferred to the press again to calibrate the dimensions. This variance in work processes has resulted in lower cost competitiveness due to the lower productivity, quality issues, and excessive operator input. The aim of this study was to establish a stable and cost - effective production system through bending / shearing process separation and facility automation.

• Nuclear Engineering and Technology
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• v.24 no.1
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• pp.75-85
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• 1992

The texture changes and their effect on the 0.2% yield strength of Zircaloy-4 sheet were examined after quenched from the ($\alpha$+$\beta$) phase temperature. When the prior ($\alpha$+$\beta$) gram size was slightly larger than that of the $\alpha$-annealed, the observed texture was similar to the $\alpha$-annealed texture having an ideal orientation of the (0001) basal pole at 30$^{\circ}$away from the normal direction toward the transverse direction. When the prior ($\alpha$+$\beta$) grain size was twice as large as that of the $\alpha$-annealed, the location of maximum basal pole intensity was distributed between the transverse and the rolling direction making an angle 15$^{\circ}$from the normal direction, and the observed texture became isotropic. It was found that the Kearns texture parameter, fr, in the rolling direction increased steadily, and fr in the transverse direction increased slightly, while fr in the the normal direction decreased with increasing heat treatment time. With a small increase in fr, the 0.2% yield strength increased drastically. The influence of texture was analyzed by deriving the Schmid orientation factors and the resolved shear stresses for the deformation systems. It was found that the large increase in the 0.2% yield strength was attributed mainly to the microstructural changes and partly to the texture changes by the ($\alpha$+$\beta$) heat treatment.

• Journal of the Korean Wood Science and Technology
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• v.46 no.1
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• pp.10-16
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• 2018

Lindera erythrocarpa is a less utilized species in Korea although that it has straight stem and it grows up to 40 cm in diameter. A proper kiln-dry schedule is required in advance to utilize an unknown species. Terazwa's quick oven-dry method was used to find it and which was confirmed by drying 25 mm thick boards in a kiln. The average green moisture content and the average green specific gravity of Lindera erythrocarpa are 72.3% and 0.53, respectively. Prospective kiln-drying conditions obtained by Terazwa's quick oven-dry method are a initial dry-bulb temperature of $50^{\circ}C$, a initial wet-bulb depression of $4^{\circ}C$ and a final dry-bulb temperature of $75^{\circ}C$, which are in a good agreement with USDA FPL kiln-dry schedule of T5-D4. 25 mm thick boards dried in a kiln with T5-D4 kiln-dry schedule did not have any severe drying defects such as honycombing and warping. A severer kiln-dry schedule of T8-C5 was developed and applied to another kiln-drying run to confirm it.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.8
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• pp.1015-1021
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• 2010

In this study, the effect of the C/SiC composition ratio on the impact damage of a reaction sintered SiC (RS-SiC) plates was evaluated. An impact test was conducted by using an air gun. The impacter used was a steel ball with a diameter of 2 mm, and the impact velocities were 113, 122, and 180 m/s. The RS-SiC plates were $20\times20\times3$ mm with different C/SiC composition ratios. The ring crack diameters damaged by a steel ball were determined using SEM images. It was observed that the maximum diameter increased with increasing impact velocity, and it rapidly changed with increasing C/SiC composition ratio because of the effect of residual Si and the variation flexural strength. Cone cracks were formed in the case of C/SiC composition ratios of 0.4~0.5, this indicated that the impact damage changed from a ring crack to a cone crack in this critical range of C/SiC composition ratios. The C/SiC composition ratio of 0.3 was determined to be the optimal ratio for the RS-SiC manufacturing process.